The fundamental doctrinal tenets of Christianity, namely that Christ is God “born in the flesh,” that his sacrificial death atones for the sins of humankind, and that his resurrection from the dead guarantees eternal life to all who believe, can be traced back to Paul — not to Jesus. Indeed, the spiritual union with Christ through baptism, as well as the “communion” with his body and blood through the sacred meal of bread and wine, also trace back to Paul. This is the Christianity most familiar to us, with the creeds and confessions that separated it from Judaism and put it on the road to becoming a new religion.[Christianity Before Paul]
But what were the original teachings of Jesus?
What we get in the letter of James is the most direct possible link to the Jewish teachings of Jesus himself. James is quite sure that the “Judge” is standing at the door, and that the kingdom of God has drawn very near (James 5:7). He warns the rich and those who oppress the weak that very soon the judgment of God will strike. James seems to be directly echoing and affirming what he had learned and passed on from his brother Jesus. It is important to note that James did not directly quote Jesus or attribute any of these teachings to Jesus by name — even though they are teaching of Jesus.
For James the Christian message is not the person of Jesus but the message that Jesus proclaimed. James’ letter lacks a single teaching that is characteristic of the apostle Paul and it draws nothing at all from the Gospel narratives. What we have preserved in this precious document is a reflection of the original apocalyptic proclamation of Jesus: the “Gospel of the kingdom of God” with its political and social implications.[Christianity Before Paul]
Thus it looks like, it was Paul who caused the shift from Jesus’ message to Jesus the person himself.